1. Field of the Invention
The present invention relates to a resin seal type semiconductor device, and a method for producing the same.
2. Description of the Related Art
Recently, in keeping with the tendency toward high density packaging of electrical appliances, there has been increased demand for thin and small-sized semiconductor devices, and the production quantity of resin seal type packages such as Ball Grid Array/Chip Size Package (BGA/CSP) has increased. In these circumstances, in order to improve BGA/CSP production or the like, a production method using package molding/saw cutting techniques has been widely used where a plurality of integrated circuit (IC) chips are fixed to one wiring substrate and sealed all together by mold resin. Thereafter, the wiring substrate is cut into separate semiconductor devices.
FIG. 2 is a cross sectional view showing an example of a conventional semiconductor device.
The semiconductor device shown in this drawing is that of BGA/CSP type produced by using package molding/saw cutting technique. An IC chip 3 is fixed onto a wiring substrate 1 by an adhesive agent 2. The wiring substrate 1 is, for example, formed of a glass/epoxy substrate having a thickness of 0.2 mm or thereabouts. Wiring patterns 1a and 1b are respectively formed on face and reverse surfaces of the wiring substrate 1 in the periphery thereof and are electrically connected to each other via a through hole 1c. 
The wiring pattern 1a formed on the face surface of the wiring substrate 1 and an electrode 3a on the surface of the IC chip 3 are connected by a wire 4 such as gold wire. The surface of the wiring substrate 1 is sealed by a mold resin 5 having a predetermined thickness so as to protect the IC chip 3 and the wire 4. A soldering ball 6 having a diameter of 0.5 mm or thereabouts is attached to the wiring pattern 1b formed on the reverse surface of the wiring substrate 1 so as to make connection with a printed circuit board or the like.
Such semiconductor devices as above are produced by the following process.
First, a wiring substrate is produced in which plural sets of wiring patterns 1a and 1b, and through holes 1c are arranged, corresponding to each of the plural IC chips 3, in transverse and vertical directions in a region around a corresponding IC chip 3. Subsequently, the plural IC chips 3 are each fixed by the adhesive agent 2 to a predetermined position on the wiring substrate, and an electrode 3a on the surface of the IC chip 3 and the wiring pattern 1a corresponding thereto are connected by the wire 4 for wire bonding.
Further, the wiring substrate on which the plural IC chips 3 are mounted is placed on a lower metallic mold heated to 170° C. or thereabouts, and a corresponding upper metallic mold is placed thereon. The mold resin 5 is injected from an injection hole formed in the upper metallic mold into an interior of the molds and a cavity formed by an inner surface of the upper metallic mold, and the wiring substrate is sealed by the mold resin 5.
After the mold resin 5 has been cured, the wiring substrate of which surface is sealed by the mold resin 5, is taken out by releasing the upper and lower metallic molds therefrom. The resin-sealed wiring substrate is cut into separate semiconductor devices corresponding to the IC chips 3 by using a cutting saw. The soldering ball 6 is attached to the wiring pattern 1b on the reverse side of each of the separate wiring substrates 1, to thereby form a complete semiconductor device. Thus, productivity markedly improves as compared with a method in which wiring semiconductor devices are separately molded one by one.
However, the above-described structure of semiconductor devices and method for producing the same, which have been conventionally known, have the following problems.
When the wiring substrate having dimensions of, for example 60 mm×180 mm, is placed on a lower metallic mold heated to 170° C. or thereabouts, the wiring substrate is warped due to heat from the lower metallic mold and a portion of the wiring substrate may be raised from the lower metallic mold. When the upper metallic mold is placed on the wiring substrate in the above-described state, there exists a problem in which the bonded wire 4 contacts the inner surface of the upper metallic mold and thereby deforms. In this regard, there is a risk of causing short-circuits due to deformed wires 4 contacting each other.